1. Field of the Invention
The present invention relates generally to magnetic heads and methods of making the same, and more particularly to read sensors having narrow track widths and high magnetoresistive sensitivities, and methods of making the same.
2. Description of the Related Art
Higher density recording needs of future direct access storage devices (DASDs) are forcing the dimensions of magnetic heads to be well into sub-micron sizes. For example, it is predicted that for 10 gigabit (Gb/in2) drives, the read head size should be about 0.5 um; for 20 Gb/in2 drives, the read head size should be about 0.35 um; for 40 Gb/in2 drives, the read head size should be about 0.17 um; and for 100 Gb/in2 drives, the read head size should be about 0.12 um. Such extreme resolutions make patterning techniques for the magnetic heads very difficult, especially for read sensors.
One conventional method of fabricating a magnetic head utilizes a common masking and milling process. A conventional lift-off mask is made of two layers, namely, a top photoresist layer and a bottom underlayer. This bi-layer lift-off mask is formed over the sensor materials in a central region. The lift-off mask may be referred to as a photoresist mask or resist mask. Ion milling is performed using the mask to remove sensor materials in end regions which surround the central region, such that a central read sensor below the resist mask is formed. Bias layers and lead layers are then deposited in the end regions and over the mask, and the resist mask is removed by dissolving the bottom underlayer. Finally, a gap layer is deposited over the read sensor and the surrounding lead layers. The above-described technique works very well in defining sensor structures down to 0.2 μm, but it shows limitations below that size.
A lead overlay structure is particularly advantageous for enhancing the performance of a read sensor and providing it with a narrow magnetic track width. A process for forming such a structure involves a first photolithography step to define the leads, and a second photolithography step plus ion milling to define the hard bias stabilization of the free layer in the read sensor at a set distance removed from the inner lead edge. However, performing two photolithography steps to define the read sensor is relatively difficult from a manufacturing point of view.
Accordingly, what are needed are improved read sensors having narrow track widths and improved methods of making the same.